A team of
international researchers has used a human vaccine to cure prostate tumors in
mice without side effects.

Richard Vile, Ph.D., study leader and Mayo Clinic immunologist, along with Alan
Melcher, Ph.D., and Peter Selby, Ph.D., both from the Cancer Research UK
Clinical Centre at St. James' University Hospital, have developed a cure for prostate cancer in mice
that also shows promise for other cancers and melanoma as well.

Scientists have attempted to accomplish this in the past, but were hindered by
the inability to isolate a diverse collection of antigens in tumor cells. This
then causes tumors to mutate and survive the body's immune system.

But Vile and his team were able to overcome this by first piecing together
parts of genetic code from human prostate tissue into a
complementary DNA (cDNA) library. The cDNA were then placed into a mob of
vesicular stomatitis viruses (VSV), which were cultured. They were then given
to the mice as a vaccine through several intravenous injections.

Tumors have a unique "fingerprint" called an antigen, which triggers
an immune system response through a molecular protein tag. By releasing the
human vaccine prostate cancer antigens into the mutated VSV vector, the mice's
T-cells were able to launch an attack. The animals' immune systems then became
familiar with the antigens expressed in the virus after being exposed to the
mutated virus, and created a potent immune response. This attacked the prostate
tumors.

Vile's immunotherapy research differed from others because it made use of
viruses as vectors for cDNA libraries. This eliminates the challenge of
isolating antigens in tumor cells because it offers an in-depth profile of the
cancer.

"Nobody really knows how many antigens the immune system can really see on
tumor cells," said Vile. "By expressing all of these proteins in
highly immunogenic viruses, we increased their visibility to the immune system.
The immune system now thinks it is being invaded by the viruses, which are expressing
cancer-related antigens that should be eliminated."

Clinical trials are expected to begin in two years.

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